1. Field of the Invention
This invention relates to a data backup system and a data backup method, especially to a data backup system and a data backup method for non-volatile storage devices.
2. Description of Related Art
With the popularity of flash memories, more and more computers and electronic products use storage devices made from flash memories, such as solid-state drives (SSDs), to replace conventional hard disk drives (HDDs). Due to limited service lives, the flash memories are subject to data backup when their service lives are about to end. FIG. 1 illustrates a conventional data backup operation of flash memory storage devices. The control unit 112 of the flash memory storage device 110 and the control unit 122 of the flash memory storage device 120 perform read and write operations on the flash memory 114 and the flash memory 124, respectively, according to their respective logical-to-physical mapping tables (hereinafter referred to as the L2P table). When an operating system on a host accesses the flash memory storage device 110 or the flash memory storage device 120, the file system module 140 refers to logical block addresses (LBAs) to obtain the logical address of a destination and issues access commands to the flash memory storage device 110 or the flash memory storage device 120 through the driver module 130. The access command contains the logical address of the destination. Then the control unit 112 or the control unit 122 translates the logical address of the destination to the physical address (PA) of the flash memory 114 or the flash memory 124 by referring to the L2P table.
Assuming that the data are about to be backed up from the flash memory storage device 110 (the source) to the flash memory storage device 120 (the destination), as indicated by the direction of the dotted line), the host keeps reading data from the flash memory storage device 110 and writing them into the flash memory storage device 120 during the backup process. As only a fixed amount of data are being read or written each time the file system module 140 accesses the flash memory storage device 110 and the flash memory storage device 120, such as 4 KB for each access, the times of read operations to completely read out the data in the flash memory storage device 110 are quite many. In addition, the data in the flash memory 114 are probably unorganized after a long use of the flash memory storage device 110, meaning that reading data out of the flash memory storage device 110 is accompanied by a huge amount of random accesses. The random access requires the control unit 112 to refer to the L2P table to translate the logical addresses to the physical addresses in each read operation, which is a time-consuming operation for the control unit 112 and therefore renders a long backup time. Moreover, in some cases where an operating system or applications may be installed in the flash memory storage device 110 as well, when a backup operation is being performed, only personal data, such as multimedia files and documents, are backed up by a user while the operation system and/or the applications are missing.